JPH01284769A - Generating device for electric signal corresponding to surface potential distribution - Google Patents

Abstract

PURPOSE:To reduce a measurement error by putting an electrode for detection close to and away from the surface of a body to be detected periodically, and measuring a voltage and resetting charges based upon a leak current according to the timing of the movement of the electrode. CONSTITUTION:Electrodes ED1-EDn for surface potential detection detect the surface potential of the body to be detected and potential voltages detected by the electrodes ED1-EDn are led out by transistors(TR) DF1-DFn for voltage detection which are scanned in order by a shift register SR and outputted as a serial signal to an output terminal 1. Those electrodes ED1-EDn are put close to and away from the surface of the body periodically and the voltage measurement by the TRs DF1-DFn and the resetting operation by reset TRs RF1-RFn are performed according to the timing of the approaching and leaving operation of the electrodes. Consequently, charges due to leakage currents of the TRs DF1-DFn are securely reset, so the measurement error is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an apparatus for generating an electrical signal corresponding to a surface potential distribution.

(Prior art) It is possible to bring a voltage detection electrode close to the surface of the object to be detected and to detect the voltage generated in the voltage detection electrode by electrostatic induction based on the surface potential of the object to be detected. This method has long been known as one of the methods for detecting the surface potential of the object to be detected.
Since the voltage detection electrode circuit in the method for detecting the surface potential of the object to be detected has a very high impedance, the voltage of the voltage detection electrode is extracted via an impedance conversion circuit. It's like that.

(Problem to be Solved by the Invention) The above-mentioned impedance conversion circuit can also use a field effect transistor as an active element, but as is well known, a field effect transistor has a connection from the drain electrode to the gate electrode. Since the leakage current exists, the leakage current charges the capacitance of the input side circuit of the gate electrode of the field effect transistor, and the potential of the gate electrode gradually increases accordingly.

Therefore, when the voltage generated by electrostatic induction corresponding to the surface potential of the object to be detected is extracted through an impedance conversion circuit using a field effect transistor, the detection operation takes a relatively long time. If the detection is carried out over a long period of time, the problem is that the detected voltage value will be inaccurate, and if the detection time is longer, the output signal will be saturated and the surface potential of the object to be detected will be reduced. Detection becomes impossible.

Therefore, in an impedance conversion circuit using field effect transistors, the capacitance of the input side circuit of the gate electrode of the field effect transistor is connected to the drain electrode.
It is necessary to discharge the charge accumulated by leakage current between the gate electrodes, and conventionally, the drain electrode and the capacitance of the input side circuit of the gate electrode of a field effect transistor are
A reset means has been used to discharge the charge accumulated by the leakage current between the gate electrodes.
When added to the input circuit of ti, the capacitance value on the input circuit side of the gate electrode of the field effect transistor increases, resulting in a decrease in detection sensitivity.In addition, even if the reset means is applied as described above, too.

The state of the output signal during the period from the time a reset is performed to the next reset is determined by the charging operation due to the leakage current between the drain electrode and the gate electrode with respect to the capacitance of the input side circuit of the gate electrode of the field effect transistor. As the voltage increases gradually, there is no solution to the problem that the detected voltage value becomes inaccurate over time. Therefore, a good solution to the above-mentioned problems has been sought.

(Means for Solving the Problems) The present invention provides a field effect transistor for voltage detection in which a voltage generated by electrostatic induction corresponding to the surface potential of a detected object is applied to a gate electrode, and A surface potential distribution comprising a reset switching means for discharging charges charged by a leakage current between the drain electrode and the gate electrode of the voltage detection field effect transistor in the capacitance of the input side circuit of the effect transistor. means for detecting the surface potential of the object to be detected using an electrode for detecting surface potential at a predetermined position close to the surface of the object to be detected; The above-mentioned reset is performed so that the distance between the potential detection electrode and the potential detection electrode is set to such a state that the voltage generated at the surface potential detection electrode due to electrostatic induction corresponds to the surface potential of the object to be detected. a generating device for generating an electric signal corresponding to a surface potential distribution, comprising means for causing a reset operation to be performed by a switching means for
A field effect transistor for voltage detection in which a voltage generated by electrostatic induction corresponding to the surface potential of the object to be detected is applied to the gate electrode, and a capacitance of the input side circuit in the field effect transistor for voltage detection as described above. A device for generating an electric signal corresponding to a surface potential distribution, which is equipped with a reset switching means for discharging charges accumulated by a leakage current between a drain electrode and a gate electrode of a field effect transistor for voltage detection. After sequentially performing the reset operation and the reset release operation by the reset switching means at a predetermined position close to the surface of the object, the distance between the surface of the object to be detected and the electrode for detecting the surface potential is adjusted. The reading operation of the detected value of the surface potential of the object to be detected is performed in such a state that the voltage generated at the ffl pole for detecting the surface potential due to electrostatic induction corresponding to the surface potential of the object to be detected is a sufficiently small voltage. a voltage detection electric field in which a voltage generated by electrostatic induction corresponding to the surface potential of a detected object is applied to a gate electrode; A reset device for discharging charges accumulated in the capacitance of the input side circuit of the effect transistor and the voltage detection field effect transistor by leakage current between the drain electrode and gate electrode of the voltage detection field effect transistor. A device for generating an electric signal corresponding to a surface potential distribution, comprising a switching means, the surface of the object to be detected by an electrode for detecting the surface potential at a first predetermined position close to the surface of the object to be detected. means for sequentially performing a potential detection operation, a reset operation by a reset switching means, and a reset release operation; means for sequentially performing an operation of detecting the surface potential of the object to be detected at a predetermined second position, a resetting operation by the reset switching means, and an operation of canceling the reset; The detection force of the surface potential of the object detected by the electrode for detecting surface potential at the position and the detection force of the surface potential of the object detected by the electrode for detecting surface potential at the predetermined second position. The present invention provides an apparatus for generating an electric signal corresponding to a surface potential distribution, which includes means for obtaining a detection force by subtracting a detection force of a surface potential of a body.

(Example) Hereinafter, with reference to the accompanying drawings, specific contents of the electric signal generating device corresponding to the surface potential distribution of the present invention will be described in detail. FIG. 1 is a block diagram showing a schematic configuration of an embodiment of an electric signal generator corresponding to the surface potential distribution of the present invention, and FIGS. A timing chart for explaining the operation of the electric signal generator; FIG. 4 is a block diagram of a part of the constituent parts of the electric signal generator corresponding to the surface potential distribution of the present invention;
FIG. 5 is a circuit side view for explaining the problems of the electrical signal generator corresponding to the surface potential distribution of the present invention, FIG. 6 is a perspective view showing an example of the configuration of the detection head, and FIG. FIGS. 8 to 12 are diagrams for explaining the operation of the waveform quantities used to explain the operation of the electric signal generator corresponding to the illustrated surface potential distribution.

FIG. 1 is a block diagram of an embodiment of an electric signal generator corresponding to the surface potential distribution of the present invention. In FIG. This detection head EDA is configured such that the distance between its voltage detection electrode ED and the surface of the detected object O is between two predetermined positions set in space. It is made to change.

In FIG. 1, the detection head EDA is a displacement drive device [BG
It is connected to the movable part 6 at M by a connecting member 4. 5 is a center holder of the movable part 6 in the displacement drive device BGM. As the displacement drive device BGM, for example, a displacement drive device configured using a voice coil motor, an electrostrictive element, or other suitable electro-mechanical conversion element can be used. By supplying the drive signal generated by the generator @SG, the voltage detection electrode ED in the detection head EDA comes close to the surface of the detected object 0, as shown in the detection head EDA at the solid line position in FIG. Or, like the detection head EDA at the dotted line position in FIG. 1, the voltage detection electrode E'D in the detection head EDA
is at a predetermined position separated from the surface of the object to be detected ○, or the detection head EDA is displaced between two predetermined positions in space. In addition, 7 is the displacement drive device fiR
B It is a permanent magnet that provides a magnetic field to the moving coil in the case of CM.

As a detection head EDA in which a plurality of voltage detection electrodes ED, ED, . . . are arranged in a predetermined arrangement pattern, for example, a configuration shown in FIG. , In Fig. 5, E Di, E
D2. E D3-E Dn are voltage detection electrodes, and these voltage detection electrodes EDI, ED2. ED3...
・EDn is an individual connection wire Ω1゜R2, Q3
... field effect transistor D for voltage detection by Qn
Fl, D F2. D F3 - Field effect transistor RF connected to the gate electrode of D Fn and used as a reset switching means 1.
RF 2. RF 3 - Connected to the drain electrode of its counterpart in RFn.

Each field effect transistor RFI, RF2 . used as the above-mentioned reset switching means. RF3...R
The gate electrode at Fn is the input terminal 2 of the reset pulse.
are commonly connected to each field effect transistor RFl, RF2 . The source electrodes of RF3 to RFn are commonly connected to a power source Vss that supplies a reference voltage to be applied to the voltage detection electrode and the gate electrode of the voltage detection field effect transistor during the reset operation.

In addition, each voltage detection field effect transistor DF described above
I, DF2. The drain electrodes of DF3 to DFn are commonly connected to the operating power supply V and supplied with a constant voltage, and each of the voltage detection field effect transistors DPI, DF2゜DF3...DFn The source electrodes of the respective switching field effect transistors SFI, SF2, SF3...SFn are connected to the drain electrodes of corresponding ones of the individual switching field effect transistors SFI, SF2, SF3...SFn, and the respective switching field effect transistors SFI
, SF2°SF3...SFn are connected in common to the output terminal 1. RQ in FIG. 5 indicates load resistance.

The individual switching field effect transistor S
Fl, S F2. Each gate electrode in SF3-3Fn receives switching pulses PL, P2 . P3...Pn is supplied, but
Switching pulses PI, P2 . As is clear from the waveform diagram illustrated in FIG. 7, P3...Pn are supplied to the clock terminal 8 of the shift register SR ((a) in FIG. 7).
By the clock signal Pc shown in FIG.
As illustrated in b) to (d), P1→ on the time axis
Shift register SR sequentially as P2→P3→...
Since the output is output from the above-mentioned individual switching field effect transistors S Fl, S F2. SF3-
One selected one of the 8 F n is sequentially turned on on the time axis.

So each individual connection line Q1. Q2. f
l3...Qn, voltage detection field effect transistors DFl, DF2 . DF3...a plurality of voltage detection electrodes EDI and ED2 connected to the gate electrode of DFn
．． ED3...The voltage corresponding to the surface potential of each of the plurality of locations of the object to be detected occurring at EDn is determined by the voltage detection field effect transistors DFl,
D F2. D F3...From the source side of D Fn,
Since the switching pulses PI, P2 . Individual switching field effect transistors S Fl, S F are turned on one after another as F3... are sequentially output.
2. From the source side of S F3-8 F n, individual voltage detection electrodes E DI, E are formed by electrostatic induction corresponding to the surface potential of each of the plurality of points on the object to be detected.
D2. A voltage corresponding to the voltage generated at E D3-E Dn is sent out to the output terminal 1 in series on the time axis.

Therefore, for example, as shown in FIG. 6, a plurality of voltage detection electrodes E DI, E D2. E D3-E Dn is 1
The detection heads and the object to be detected, which are arranged in a straight line, are connected to the plurality of voltage detection electrodes EDI as described above.
, ED2. When ED3-EDn are relatively moved in a direction perpendicular to the direction in which they are aligned, a time-series electric signal corresponding to a two-dimensional charge image formed on the object to be detected is output from output terminal 1. It will be sent to

The above-mentioned detection head shown in FIG. 6 includes a plurality of voltage detection electrodes E Di, E D2. E D3 = E Dn and connection lines Q1 to Qn are attached to base B using well-known thin film technology.
This is a configuration in which P is formed. In the explanation so far, the surface potential of the object to be detected is detected by the voltage detection electrode provided on the detection head, and the surface potential is supplied to the gate electrode of the voltage detection field effect transistor via the connection line. However, in practice, the gate electrode of the voltage detection field effect transistor may also be used as the voltage detection electrode.

In the above-mentioned electric signal generating device corresponding to the surface potential distribution shown in Figure 5, a voltage corresponding to the surface potential of the object to be detected is generated at a minute voltage detection electrode by an electrostatic induction phenomenon. Therefore, the voltage detection electrodes EDI, ED2° ED3...EDn and the voltage detection field effect transistors D Fl, D F2. DF
3=Connection line Q connecting with D Fn 1. Q
2. Q3...nn, if a voltage is generated by electrostatic induction based on an external electric field, it will not be possible to generate an electric signal that accurately corresponds to the charge image of the detected object, but this problem are voltage detection electrodes EDI, ED2. ED
3-EDn and voltage detection field effect transistor D Fl
, D F2. Connection line fi connecting between D F3 and D Fn 1. Q2. Q3...nn is connected to the connecting wire Q1 so that voltage is not generated due to electrostatic induction based on an external electric field. Q2. y 3...Qn
Electrostatic shielding S may be applied to the portion.

Also, an electric field due to charges on the surface of the object to be detected 0 to be detected by a certain voltage detection electrode.

Even when adjacent voltage detection electrodes are detected, it may not be possible to generate an electrical signal that accurately corresponds to the charge image of the object to be detected. This can be solved by providing an electrostatic shield S in the area.

Now, as shown in the first diagram, the detection head EDA is connected to the object to be detected.
The switching pulses PI, P2 . The individual switching field effect transistors S Fl, S F2 . are turned on one after another as F3 . . . are sequentially output. SF
3-8 From the source side of Fn, individual voltage detection electrodes EDI are formed by electrostatic induction corresponding to the surface potentials of individual locations aligned in the x direction at multiple locations on the object to be detected,
ED2. ED3: The voltage corresponding to the voltage generated at EDn is sent to the output terminal 1 as one block of time-series signals arranged in series on the time axis, and the voltage corresponding to the voltage generated at EDn is sent to the output terminal 1. E Di, E D2. E D3
-E A reset pulse Pr is supplied to input terminal 2 every time one block of time-series signals in which voltages corresponding to all the voltages generated at Dn are arranged in series on the time axis is obtained. When the reset switching means is operated and the above-mentioned reset pulse is supplied, all voltage detection types +4! EDI, ED2. ED3...E
The potential of Dn and the potential of the gate electrodes of all the voltage detection field effect transistors DPI, DF2, . . . are set to the reset power supply voltage Vss.

The detection head EDA is reset as described above when it finishes outputting one block of time-series signals from the detected object O in the arrow X direction shown in FIGS. 8(a) and (b). After the detected object O and the detection head EDA are relatively moved a predetermined distance in the direction of the arrow Y in FIG. 8(a), the arrow X at the new position is moved.
By repeating the process of outputting one block of time-series signals from the detected object O in the direction and resetting them as described above when the output is finished, the two-dimensional charge on the surface of the detected object O is calculated. The output signal corresponding to the image is sent to the detection head ED.
It is sent out from output terminal 1 of A.

A-A line, B-B line, C shown in FIG. 8(b)
-C line, D-D line, etc. are examples of lines in the X direction in which one block signal is sequentially generated by the detection head EDA at different positions in the Y direction of the detected object 0.

To detect the surface potential of the object to be detected O, the voltage detection electrode ED is brought close to the surface of the object to be detected ○, and based on the surface potential of the object to be detected 0, the voltage detection electrode ED is moved by electrostatic induction. When the generated voltage is detected, the output voltage Vout sent from the source electrode side of the voltage detection field effect transistor DF to the output terminal 1 of the detection head EDA is as follows.
Assume that the value of the capacitance of the input circuit side of the gate electrode of the voltage detection field effect transistor DF is Cin.

If the capacitance between the surface of the detected object O and the voltage detection electrode ED is C, and the surface potential of the detected object 0 is Vf, then as shown in the equation shown in FIG. expressed.

Furthermore, the voltage detection electrode circuit configured as described above has extremely high impedance.

When taking out the voltage of the voltage detection electrode ED, it is taken out via an impedance conversion circuit, and the fifth
In the detection head illustrated in the figure as well, the voltage detection electrode ED (subscript omitted) is connected to the gate electrode of the voltage detection field effect transistor DF (subscript omitted), and the detected voltage is connected to the source. However, if the impedance conversion circuit used to take out the voltage of the voltage detection electrode ED is configured using a field effect transistor, the drain of the field effect transistor Due to the leakage current from the electrode to the gate electrode, the capacitance of the input side circuit of the gate electrode of the field effect transistor is charged, and the potential of the gate electrode gradually increases, and the voltage is applied to the surface of the object to be detected. Since it is superimposed on the detected voltage value generated by electrostatic induction corresponding to the potential, the charge accumulated by the leakage current between the drain electrode and the gate electrode is discharged into the capacitance of the input side circuit of the gate electrode of the field effect transistor. Resetting means are applied in order to do so.

As mentioned above, the capacitance of the input side circuit of the gate electrode of the field effect transistor is charged by the leakage current between the drain electrode and the gate electrode of the field effect transistor, so that the potential of the gate electrode gradually increases over time. Figure 10 illustrates the state in which the electric charge accumulated in the capacitance of the input side circuit of the gate electrode of the field effect transistor by the leakage current between the drain electrode and the gate electrode is discharged by the reset means. As shown in (,) in Fig. 10, it is a switch used as the SWr beam setting means, and C1n- is the switch on the input circuit side of the gate-electrode of the voltage detection field effect transistor DF. is the capacitance, i is the leakage current between the drain electrode and the gate electrode of the voltage detection field effect transistor DF, and FIG. 10(b) shows the switch SWr in FIG. 10(a). In the on state (reset state m>), the capacitance Cin on the input circuit side of the gate electrode of the voltage detection field effect transistor DF is
After discharging the charges accumulated in the switch SW
When r is turned off, the capacitance fLci on the input circuit side of the gate electrode of the voltage detection field effect transistor DF increases.
This shows a state where n is charged again by the leakage current i between the drain electrode and the gate electrode, and the potential of the gate electrode of the voltage detection field effect transistor DF is gradually increased.

12(a) and (b) show that the MI capacitance fcin on the input circuit side of the gate electrode of the voltage detection field effect transistor DF is charged by the leakage current i between the drain electrode and the gate electrode as described above. The reset operation in response to the rise in potential of the gate electrode of the voltage detection field effect transistor DF caused by the voltage detection ffi electrode ED
is located (for example, in (b) of Figure 8, A-A
This is an explanatory diagram of the case where the detection is performed at the position of the line or the location indicated by the arrow in Figure 12 (a) indicating reset, and O in Figure 12 (a) is the object to be detected. , and the ED shown above the detected object ○ described above.
is a voltage detection electrode, and the graph shown below the object to be detected O described above shows the distribution state of the surface potential of the object to be detected 0.

FIG. 12(b) shows the detection of the surface potential of the detected object 0 having the surface potential distribution as shown in FIG. 12(a). The voltage detection type tbED shown above the body 0 has been reset at the position indicated as reset in the figure (the position where the reset pulse Pr is displayed in Fig. 12(b)). 12 (a) and (b). The symbols a and b are symbols for indicating the correspondence between mutually corresponding parts.

The position where the voltage detection IIT pole ED is reset in (a) of FIG. 12 corresponds to the position of the detection head EDA on the line A-A in (b) of FIG. Therefore, the potential of the voltage detection electrode ED is set to the reset voltage Vss shown in (Q) of FIG. 8 and (b) of FIG. 12.

As mentioned above, the reset operation in response to the rise in potential of the gate electrode of the voltage detection field effect transistor DF is performed as follows.
The voltage detection electrode ED is located in a portion of the object O to be detected where the electric field of the charge image on the surface does not reach.
After the voltage detection electrode ED is set to the reset voltage Vss by the reset operation, the voltage detection electrode ED is moved to the detection position of the surface potential based on the charge image of the detected object 0, and the voltage detection electrode ED detects the surface potential. The voltage applied is the first
The surface potential shown in FIG. 12(b) corresponds to the surface potential due to the charge image of the object to be detected 0 shown in FIG. 2(a).

However, the reset operation in response to a rise in the potential of the gate electrode of the voltage detection field effect transistor DF
A state in which the voltage detection electrode ED is located in a part where the electric field of the charge image on the surface does not reach (for example, (b
), or at the location indicated by the arrow in FIG. Since the head EDAti is performed in a separate state, the above-mentioned reset operation is performed when the detected object
It is performed only once after the detection of all the charge images on the object, 0, is completed, but since it takes a relatively long time to detect all the charge images on the object to be detected, The capacitance Cin of the gate electrode of the voltage detection field effect transistor DF on the input circuit side may be charged by the leakage current i between the drain electrode and the gate electrode, and the voltage detection force may become saturated.

In order to solve the above-mentioned problem, the reset operation in response to the increase in the potential of the gate electrode of the voltage detection field effect transistor DF, for example, is performed as shown in FIG. 8(b).
The detection may be performed every time the detection of the surface potential of the object to be detected 0 at the position of each line such as -Bi, C-C line, and D-DIiA is completed.

However, as mentioned above, the reset operation in response to the rise in the potential of the gate electrode of the voltage detection field effect transistor DF is caused by, for example, the line B-B, line C-C in (b) of FIG.
If the test is carried out in a part where an electric field is present due to the surface potential distribution of the detected object O, the C-C line, D-D line, etc. in (b) of Fig. 8. The detected voltage value at the position of each line does not correspond to the surface potential of that part, but the voltage value detected before being reset.

A problem arises in that the voltage value is a difference from the voltage value detected after being reset.

(d), (8) in Figure 8 and Cc in Figure 12, ), (
(d) is a diagram used to explain the above-mentioned problem, and (d) of FIG.
shows the detected voltage output in the X direction at the B-B line position of
Furthermore, the curve shown by the solid line in FIG.
Next, the detection head EDA detects C-C in the detected object 0.
This is the detected voltage output when the potential distribution in the X direction is detected at the line position, and the detected voltage output shown by the solid curve in (e) of FIG.
The voltage distribution shown by the dotted line in (8) of FIG. 8, which corresponds to the actual potential distribution at the C--C line position, is not shown.

That is, the detected voltage output shown by the solid curve in FIG. 8(e) corresponds to the actual potential distribution at the C-C line position of the detected object ○, which is shown in parentheses in FIG. The voltage distribution shown by the dotted line and the detected voltage output shown in FIG. 8(d) which shows the detected voltage output in the X direction at the B-B line position of the detected object O by the detection head EDA This is the voltage difference between

12(c) and (d) show that the capacitance Cin on the input circuit side of the gate electrode of the voltage detection field effect transistor DF is charged by the leakage current i between the drain electrode and the gate electrode, as described above. The voltage detection electrode ED is located in the area where the electric field of the charge image on the surface of the detected object O extends, and the reset operation in response to the rise in potential of the gate electrode of the voltage detection field effect transistor DF caused by the FIG. 12 is an explanatory diagram of the case where the process is carried out in the state (for example, the location indicated by the position of point a in (c) of FIG. 12),
In FIG. 12(c), 0 is the object to be detected, and
The ED shown above the detected object 0 is a voltage detection electrode, and the graph shown below the detected object O shows the distribution state of the surface potential of the detected object O. ing.

FIG. 12(d) shows the detection of the surface potential of the detected object 0 having the surface potential distribution as shown in FIG. 12(c). The voltage detection electrode ED shown above the body O is at the point where the word "reset" is displayed in the figure. a The time of the detected voltage when the voltage detection electrode ED is moved from the left to the right after resetting at the position a where the reset pulse Pr is displayed in (d) of Fig. 12 The state of change on the axis is shown, and the symbols a and b in FIGS. 12(c) and 12(d) are symbols for indicating the correspondence between mutually corresponding parts.

In (c) of FIG. 12, the reset operation was performed on the voltage detection electrode ED! ! a corresponds to the position of the detection head EDA in FIG. 8(b), for example, on the line B-B, and due to the above reset, the potential of the voltage detection electrode ED is
The reset voltage Vss is set as shown in FIG. 8(d) and FIG. 12(d).

Therefore, as mentioned above, the reset operation in response to the potential rise of the gate electrode of the voltage detection field effect transistor DF is
This is performed while the voltage detection electrode ED is located in the part of the detected object O where the electric field of the charge image on the surface extends, and after the voltage detection electrode ED is set to the reset voltage Vss by the reset operation. The potential distribution detected by the voltage detection electrode ED when the above reset operation is canceled and the voltage detection electrode ED is then moved to the next detection position of the surface potential based on the charge image of the detected object O is as follows. 12th
The voltage distribution as shown by the dotted line curve in FIG. 12(d), which corresponds to the surface potential due to the charge image of the detected object ○ shown in FIG. The voltage at point a where the reset voltage is applied appears as a voltage distribution as shown by the solid curve in FIG. 12(d) when the voltage is set to the reset voltage Vss.

(a) in FIG. 11 shows the state when the reset operation is performed at point a on the detected object 0 in (c) in FIG. 12, and (b) in FIG. The figure shows a state in which the reset operation is canceled after the reset operation is performed at point a on the detected object O in (c) of the figure. If we look at the operation mode shown in (a) and (b) of FIG. 11, we can see that the voltage detection field effect transistor D
The reset operation in response to the rise in potential of the gate electrode of F is performed with the voltage detection electrode ED located in the part of the detected object 0 to which the electric field of the charge image on the surface extends, and the voltage detection electrode ED is After the reset voltage is set to Vss, the reset operation is canceled, and then, when the voltage detection electrode ED is moved to the next detection position of the surface potential based on the charge image of the detected object O, the voltage detection electrode ED It can be easily understood that the potential distribution detected by the voltage distribution appears as a voltage distribution as shown by the actual W & curve shown in FIG. 12(d).

The electric signal generation device corresponding to the surface potential distribution of the present invention shown in FIG. In addition, the reset operation in response to an increase in the potential of the gate electrode due to leakage current between the drain and gate in the voltage detection field effect transistor DF is performed, for example, as shown in FIG. The detection voltage is saturated by performing this every time the detection of the surface potential of the object O at the position of each line such as the line B-B, line c-C, and line D-D in (b) is completed. The timing of voltage detection, the start of reset operation, and the timing of release of reset operation when
The voltage detection electrode ED and the detected object O are set as shown in FIG. 2 in relation to the above-mentioned spacing, and the voltage detected at that time corresponds to the surface potential distribution of the detected object. 1, for example, the object to be detected at the position of each line such as line B-B, line C-C, and line D-D in FIG. 8(b). The timing of voltage detection, the timing of starting the reset operation, and the timing of canceling the reset operation when the reset operation is performed every time the detection of the surface potential of the head is completed in order to prevent the detection voltage of the detection head from becoming saturated. The settings are made as shown in (b) and (c) of FIG. 2 in relation to the change in the distance between the voltage detection electrode FD and the detected object 0 shown in (a) of the figure. , a field effect transistor for voltage detection in which a voltage generated by electrostatic induction corresponding to the surface potential of the object to be detected is applied to the gate electrode, and a capacitance of the input circuit in the field effect transistor for voltage detection; A device for generating an electric signal corresponding to a surface potential distribution, which is equipped with a reset switching means for discharging the electric charge charged by a leakage current between the drain electrode and the gate electrode of a field effect transistor for detecting voltage. A means for detecting the surface potential of the object to be detected using an electrode for detecting surface potential at a predetermined position close to the surface of the body; The reset operation by the above-mentioned reset switching and means is performed so that the voltage generated on the electrode for detecting the surface potential due to electrostatic induction in correspondence with the surface potential of the object to be detected is set to a sufficiently small voltage. For example, as shown in the lines BB, C-C, and D-D in FIG. 8(b), The timing of voltage detection, the start of the reset operation, and the reset operation when the reset operation is performed every time the detection of the surface potential of the detected object O at the position of each line is completed to prevent the detection voltage of the detection head from becoming saturated. The timing of release is shown in FIG. 2(d) and (e) in relation to the change in the distance between the voltage detection electrode ED and the detected object 0 shown in FIG. 2(a). A field effect transistor for voltage detection is configured as shown in FIG. The electrostatic capacitance of the side circuit is provided with a reset switching means for discharging the electric charge charged by the leakage current between the drain electrode and the gate electrode of the voltage detection field effect transistor. In the signal generating device, after sequentially performing the reset operation and the reset 'M release operation by the reset switching means described above at a predetermined position close to the surface of the object to be detected, the surface potential of the object to be detected is The distance between the detection electrode and the surface of the object to be detected is such that the voltage generated at the electrode for detecting the surface potential due to electrostatic induction is a sufficiently small voltage corresponding to the surface potential of the object to be detected. The apparatus may be configured as an electric signal generating apparatus corresponding to the surface potential distribution, comprising means for reading out the detected value of the electric potential, or, for example, as shown in FIG. 8 (b).
), the detection voltage of the detection head is saturated by performing a reset operation every time the detection of the surface potential of the object to be detected 0 at the position of each line such as B-84%, c-c line, and D-D line is completed. The timing of voltage detection when the voltage detection is disabled and the timing of the start of the sector operation and the release of the reset operation are determined by the voltage detection timing shown in (a) of Figure 3 (same as (a) of Figure 2). By setting the distance as shown in FIG. 3(b) in relation to the manner in which the distance between the electrode ED and the object to be detected 0 changes, the voltage generated by electrostatic induction corresponds to the surface potential of the object to be detected. A voltage detection field effect transistor in which a voltage is applied to the gate electrode, and a leakage current between the drain electrode and gate electrode of the voltage detection field effect transistor in the capacitance of the input side circuit of the voltage detection field effect transistor. and a reset switching means for discharging the charge charged by the surface potential distribution and a reset switching means for discharging the charge charged by the surface potential distribution. means for sequentially performing the detection operation of the surface potential of the object to be detected by the detection electrode, the reset operation and the reset release operation by the reset switching means; A detection operation of the surface potential of the object to be detected by an electrode for detecting the surface potential at a predetermined second position spaced apart from the surface of the object to be detected, and a reset operation and a reset release operation by the reset switching means. means for sequentially performing the above steps, a means for detecting the surface potential of the object to be detected detected by the surface potential detection electrode at the above-described first position, and the above-described predetermined detection force. and means to obtain the detection force by subtracting the detection force of the surface potential of the object to be detected detected by the surface potential detection electrode at the second position where the surface potential is detected. It is configured as an electrical signal generator.

The electric signal generating device corresponding to the surface potential distribution of the present invention shown in FIG. 1 is, for example, the line BB in FIG.
Voltage detection timing when the detection voltage is not saturated by being performed every time the detection of the surface potential of the detected object ○ at the position of each line such as the C-C line and the D-D line is completed. The timing of starting the reset operation and canceling the reset operation are shown in FIG. (b) and (c), the displacement drive bag [BGM shown in FIG. As shown in the solid line position of the detection head EDA in Fig. 1, when the voltage detection electrode ED in the detection head EDA is brought close to the surface of the detection object 0, the potential of the detection head EDA corresponds to the surface potential of the detection object 0 The voltage generated in the voltage detection electrode ED by electrostatic induction is outputted,
In addition, the displacement drive bag @BGM is activated by the drive signal generated by the signal generator SG, and the detection head E at the dotted line position in FIG.
As shown in Fig. 9, the voltage detection electrode ED in the detection head EDA is sufficiently separated from the surface of the detected object O, that is, the distance between the voltage detection electrode ED and the detected object O, as shown in Fig. 9. The capacitance value C in the formula shown in is Cin
in a state where the voltage generated by electrostatic induction on the voltage detection electrode ED becomes a sufficiently small voltage corresponding to the surface potential of the object O to be detected. The reset operation as described above is performed, and there is also an electric signal generating device corresponding to the surface potential distribution of the present invention shown in FIG.

For example, (b) in Figure 8! To avoid saturation of the detection voltage, this is done every time the detection of the surface potential of the object to be detected 0 at the position of each line such as B-Ba, c-c line, and D-Dg is completed. The timing of voltage detection, the start of the reset operation, and the timing of the cancellation of the reset operation when When the settings shown in FIG. 2 (d) and (e) are implemented in connection with the above, the displacement drive device BGM shown in FIG. As shown in the solid line position of the detection head EDA in FIG.
After the above-described reset operation is performed in a state in which the voltage detection electrode ED in the detection head EDA is brought close to the surface of the object to be detected ○, the reset operation is canceled, and then the displacement drive bag The fiBCM uses the drive signal generated by the signal generator SG to measure the distance between the voltage detection electrode ED and the detected object O as shown in FIG. 9 by the detection head EDA at the dotted line position in FIG. The capacitance value C in the equation is changed until it becomes much smaller than the value of Cin, and a static [voltage generated by induction] is applied to the voltage detection electrode ED corresponding to the surface potential of the object to be detected. In a state where the voltage detection electrode ED in the detection head EDA is sufficiently separated from the surface of the detected object 0 so that a sufficiently small voltage is generated, the detection head EDA
When the reset operation is canceled when the voltage detection electrode ED is close to the surface of the detected object O,
A voltage generated at the voltage detection electrode ED due to electrostatic induction is outputted in correspondence with the surface potential of the electrode.

The arrow U in FIG. 1 is used to show how the distance between the voltage detection electrode ED and the detected object 0 changes, and the arrow U in FIG. , (d) shows the period in which the voltage detection electrode ED is located at a predetermined position where the distance between the voltage detection base piED and the detected object 0 is small, and the period in which the voltage detection electrode ED and the detected object 0 are separated. This is an example of a case where the entire period in which the voltage detection electrode ED is located at a predetermined position with a large interval is used for the voltage detection operation and the reset operation.
(c) and (e) in (b) to (e) of the figure indicate the period during which the voltage detection electrode ED is located at a predetermined position where the distance between the voltage detection electrode ED and the detected object 0 is small. The voltage detection operation and the reset operation are performed only during a part of the period in which the voltage detection electrode ED is located at a predetermined position where the distance between the voltage detection electrode ED and the detected object 0 is large. This is an example of a case.

In addition, as shown in (c) and (e) of Fig. 2, the voltage detection electrode E
Part of the period during which the voltage detection electrode ED is located at a predetermined position where the distance between D and the detected object O is made small, or during a predetermined period where the distance between the voltage detection electrode ED and the detected object O is made large. If the voltage detection operation is performed only during a part of the period during which the voltage detection electrode ED is located at the position, the electric field will increase due to leakage current from the drain electrode to the gate electrode of the field effect transistor during the detection period. Voltage detection can be performed within a range in which the amount of change in potential of the gate electrode due to charging of the capacitance of the input side circuit of the gate electrode of the effect transistor is small.

The electric signal generating device corresponding to the surface potential distribution of the present invention shown in FIG. 1 is, for example, the line BB in FIG.
Voltage detection timing when the detection voltage is not saturated by being performed every time the detection of the surface potential of the detected object O at the position of each line such as the C-C line and the D-D line is completed. The timing of starting the reset operation and canceling the reset operation are shown in FIG. 2 (b) and (c) and the change in the distance between the voltage detection electrode ED and the detected object 0 shown in (a) of FIG. The polarity of the output voltage is reversed when the settings are set as shown in FIG. 2 (d) and (e), but in any case, the present invention shown in FIG. In a device for generating an electric signal corresponding to the surface potential distribution, a voltage corresponding to the surface potential distribution of the object to be detected is detected.

Next, an electric signal generating device corresponding to the surface potential distribution of the present invention shown in FIG.
The voltage when the detection voltage is prevented from being saturated by being performed every time the detection of the surface potential of the detected object 0 at the position of each line such as the B line, the C-C line, and the D-D line is completed. The timing of detection, the start of reset operation, and the timing of release of reset operation are shown in (a) (second
Voltage detection electrode ED shown in (same as (a) in the figure)
When the setting is performed as shown in FIG. 3(b) in relation to the manner in which the distance between The displacement drive device BGM in FIG. 1 is located at the position (first position) of the detection head EDA shown by the solid line in FIG. The first position is close to the surface of the detection head EDA, where the distance between the voltage detection electrode ED and the detected object O is large. When the detection head EDA is displaced between the two positions (the second position), the detection head EDA is moved between the first position and the second position. Even if there is, the detection head ED
In A, as shown in FIG. 3(b), a voltage detection operation, a reset operation, and a reset operation canceling operation are sequentially performed.

In this case, in the detection head EDA, B-BglC-CI in FIG. 8(b) for the detected object O! ,
Because the detection head EDA sequentially performs a voltage detection operation, a reset operation, and a reset operation cancellation operation at each position of each line such as the D-D line, as shown in FIG. 3(b), The signal output from the detection head EDA is shown in Fig. 3 (
Q), i.e., the signal in the state shown in (Q) in FIG.
In b), the signals that are sequentially output on the time axis corresponding to the position of each line such as the B-B line, C-C line, and D-D line are in a state where the polarity of the signal is sequentially inverted. The reason for such a signal can be easily understood from the explanation with reference to FIG.

FIG. 4 shows the ((
A signal processing circuit for the signal in the state shown in c), that is, the signal in the state in which the polarity of the sequential signals arranged on the time axis in the time series signal is inverted,
In the figure, 9 is an input terminal of the signal processing circuit, SW is a changeover switch whose movable contact is alternately switched between two fixed contacts a and b every horizontal scanning period, and IHDL is a delay circuit for the aqua regia scanning period. , PRC is a polarity inversion circuit, ADD is an addition circuit, and 10 is an output terminal.

The signal in the state shown in FIG. 3(c) output from the detection head EDA to the input terminal 9 of the signal processing circuit shown in FIG. 4, that is, the polarity of the signal on the time axis. A signal is supplied in which the signals are sequentially inverted, and
When the movable contact of the changeover switch SW performs a switching operation synchronized with the repetition period of the signal supplied to the input terminal 9 according to the changeover control signal supplied to the control terminal 3, the fixed contact of the changeover switch SW an output signal from a delay circuit IHDL for one horizontal scanning period connected to a;
Two signals, including the output signal from the polarity inversion circuit PRC, are supplied to the addition circuit ADD.

In the two signals supplied to the adder circuit ADD,
The detection voltages corresponding to the surface potential of the object to be detected are mutually supplied as in-phase signals to the adder circuit ADD.
Since the residual leakage currents included in the signals are signals with opposite phases, they are output from the output terminal 10 by the adder circuit ADD.
The signal sent to is in a state in which the residual leakage current component contained in the two signals supplied to the adder circuit ADD is canceled, and the detected voltage corresponding to the surface potential of the detected object is It's doubled.

In this way, the signal output from the output terminal 10 of the signal processing circuit shown in FIG. 4 has the leakage current component generated in the signal during successive reset operations removed in a good manner.

(Effects of the Invention) As is clear from the detailed explanation above, the electric signal generating device corresponding to the surface potential distribution of the present invention is capable of generating electric signals generated by electrostatic induction corresponding to the surface potential of the detected object. A voltage detection field effect transistor in which a voltage is applied to the gate electrode, and a leakage current between the drain electrode and gate electrode of the voltage detection field effect transistor in the capacitance of the input side circuit of the voltage detection field effect transistor. An electrode for detecting the surface potential at a predetermined position close to the surface of the object to be detected; means for detecting the surface potential of the object to be detected, and detecting the surface potential by electrostatic induction by adjusting the distance between the surface of the object to be detected and the electrode for detecting the surface potential to correspond to the surface potential of the object to be detected. and means for causing the above-mentioned reset switching means to perform a reset operation such that the voltage generated at the electrode is sufficiently small. , and a voltage detection field effect transistor in which a voltage generated by electrostatic induction corresponding to the surface potential of the detected object is applied to the gate electrode;
Reset switching means for discharging charges accumulated in the capacitance of the input side circuit of the voltage detection field effect transistor by a leakage current between the drain electrode and the gate electrode of the voltage detection field effect transistor. In the equipped electric signal generation device corresponding to the surface potential distribution, after sequentially performing the reset operation and reset release operation by the reset switching means at a predetermined position close to the surface of the detected object, The distance between the surface of the object to be detected and the electrode for detecting surface potential is set to a voltage that is sufficiently small so that the voltage generated at the electrode for detecting surface potential by electrostatic induction corresponds to the surface potential of the object to be detected. a generating device for generating an electrical signal corresponding to a surface potential distribution, comprising a means for reading out a detected value of the surface potential of the object to be detected in such a state; a voltage detection field effect transistor in which a voltage generated by electrostatic induction is applied to the gate electrode; - In a device for generating an electrical signal corresponding to a surface potential distribution, which is equipped with a reset switching means for discharging charges accumulated by leakage current between gate electrodes, a predetermined Detection operation of the surface potential of the object to be detected by the surface potential detection electrode at the first position; Detection operation of the surface potential of the object to be detected at a predetermined second position where the potential detection electrode is separated from the surface of the object to be detected, and reset operation and reset release operation by the reset switching means. means for sequentially performing the above steps, a means for detecting the surface potential of the object to be detected detected by the surface potential detection electrode at the above-described first position, and the above-described predetermined detection force. and means to obtain the detection force by subtracting the detection force of the surface potential of the object to be detected detected by the surface potential detection electrode at the second position where the surface potential is detected. Since the device is an electric signal generator, the electric signal generator corresponding to the surface potential distribution of the present invention requires a gutter structure of an impedance conversion circuit used to extract voltage from a voltage detection electrode circuit having a high impedance. When a field effect transistor is used, leakage current from the drain electrode to the gate electrode charges the capacitance of the input side circuit of the gate electrode of the field effect transistor, causing the potential of the gate electrode to gradually rise. Even if the reset operation applied to prevent saturation of the output voltage due to the phenomenon of shifting is performed in the region where the charge image exists on the object to be detected, it is possible to easily obtain the voltage detection force in the correct state. In addition, during the period from the time a reset is performed until the next reset, the detection voltage due to the charging operation due to the leakage current between the drain electrode and the gate electrode with respect to the capacitance of the input side circuit of the gate electrode of the field effect transistor. The problem that the detected voltage value becomes inaccurate over the course of one hour due to the increase in voltage can be easily solved, and the various problems of the prior art described above can be satisfactorily solved by the present invention.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of an electric signal generation device corresponding to the surface potential distribution of the present invention, and FIGS. 2 and 3 are generation of electric signals corresponding to the surface potential distribution of the present invention. A timing chart for explaining the operation of the device, FIG. 4 is a block diagram of a part of the constituent parts of the electric signal generator corresponding to the surface potential distribution of the present invention, and FIG. 5 is a diagram corresponding to the surface potential distribution of the present invention. 6 is a perspective view showing a configuration example of the detection head; FIG. 7 is an electrical signal generator corresponding to the surface potential distribution shown in FIG. 5. The waveform diagrams used to explain the operation of FIGS. 8 to 12 are diagrams for explaining the operation. 0... Detected object, DF... Field effect transistor for voltage detection, F D, E Dl, E D2. E D3-E
D++-voltage detection electrode, Cin...capacitance on the input circuit side of the gate electrode of the voltage detection field effect transistor DF, SWr...switch used as a reset means, C...detected Electrostatic capacitance between the surface of the body ○ and the voltage detection type ED, RF, RFd... Field effect transistor used as a reset switching means, Ru, RQ... Load resistance, EDA...・
Detection head in which a plurality of voltage detection electrodes ED, ED... are arranged in a predetermined arrangement pattern, ADD... addition circuit, Q 1. n2. Q3~On-connection line, R
Fl. RF2. RF3 to RFn... Field effect transistors used as switching means for reset, SF1,
SF2. SF3~SFn... Switching field effect transistor, SR... Shift register, BP
...base body, BGM...displacement drive device, SW...changeover switch, PRC...polarity reversal circuit, 1.10...
- Output terminal, 2... Input terminal of reset pulse Pr,
4... Connecting member, 5... Center holder of movable part 6 in displacement drive device 1BGM, 6... Movable part, 7...
Permanent magnet that provides a magnetic field to the moving coil in the case of the displacement drive BGM, (b) Stone 8 (C) Procedural amendment is the formula) July 28, 1985 Kunio Ogawa, Commissioner of the Patent Office, Case 1 Indication of 1986 Patent Application No. 113305 2, Name of invention: Surface potential distribution and corresponding electrical signal generator 3, Relationship with the person making the amendment Patent Applicant Location: Moriya-cho, Kanayō-ku, Yokohama-shi, Kanagawa Prefecture 3-12 Name (432) Victor Company of Japan Co., Ltd. 4, Agent Address Tokyo Parts Ward 3-4-19-915 Facsimile 03 (472) 2257-5 Date of Amendment Order (Method) % (Formula %) 6. Subject of amendment: Drawing (Figure 2) 7. Contents of amendment: The attached drawing, Figure 2, shall be amended as shown in the attached sheet.

Claims (1)

[Scope of Claims] 1. A field effect transistor for voltage detection, in which a voltage generated by electrostatic induction corresponding to the surface potential of a detected object is applied to the gate electrode, and an input side of the field effect transistor for voltage detection; An electric signal corresponding to a surface potential distribution, which is provided with a reset switching means for discharging the electric charge charged by the leakage current between the drain electrode and the gate electrode of the voltage detection field effect transistor in the capacitance of the circuit. In the generating device, means for detecting the surface potential of the object to be detected using an electrode for detecting surface potential at a predetermined position close to the surface of the object to be detected, and Reset by the above-mentioned reset switching means by adjusting the distance between the electrode and the electrode so that the voltage generated on the electrode for detecting the surface potential by electrostatic induction is set to a sufficiently small voltage corresponding to the surface potential of the object to be detected. a voltage generated by electrostatic induction corresponding to the surface potential of the object to be detected, which is applied to the gate electrode; In order to discharge the charge accumulated by the leakage current between the drain electrode and the gate electrode of the voltage detection field effect transistor in the capacitance of the input side circuit of the voltage detection field effect transistor and the voltage detection field effect transistor. In a generating device for generating an electric signal corresponding to a surface potential distribution, which is equipped with a reset switching means, a reset operation and a reset release operation are performed by the reset switching means at a predetermined position close to the surface of the detected object. After sequentially performing A generating device 3 for generating an electric signal corresponding to a surface potential distribution, comprising a means for reading out a detected value of the surface potential of the detected object in a state where the voltage is sufficiently small; A field effect transistor for voltage detection, in which a voltage generated by electrostatic induction corresponding to the surface potential of the body is applied to the gate electrode; A device for generating an electric signal corresponding to a surface potential distribution, which is equipped with a reset switching means for discharging charges accumulated by a leakage current between a drain electrode and a gate electrode of a field effect transistor, Detection of the surface potential of the object to be detected by the surface potential detection electrode at a predetermined first position close to a means for detecting the surface potential of the object to be detected at a predetermined second position where the electrode for detecting the surface potential is separated from the surface of the object to be detected, and a resetting operation by means of a switching means for resetting. and means for sequentially performing the reset release operation; and a means for detecting the surface potential of the object to be detected detected by the surface potential detection electrode at the predetermined first position; , means for obtaining the detection force by subtracting the detection force of the surface potential of the object to be detected detected by the surface potential detection electrode at the predetermined second position. Electrical signal generator corresponding to potential distribution